The Everglades National Park – Evolution of the Everglades ... · The Everglades National Park – Evolution of the Everglades Peatland Stephanie Möller TU-Bergakademie Freiberg

The Everglades National Park – Evolution of the Everglades Peatland Stephanie Möller TU-Bergakademie Freiberg Abstract. Florida is the second leading producer of peat in the United States. Davis (1946) classified peat depositions of Florida into eight types, based on location. The second type are large, nearly flat, poorly drained areas like the Everglades adjacent to this paper. The Everglades National Park is an interdependant hydrologic system with its wetland environment developed in recent geologic time controlled by globally and interrelated forces: climate and sea level. The Evolution of the Everglades peatland began during the past 5000 supported by a freshwater wetland system of saisonal flooding with marshes and scattered tree islands. The rate of accumulation of peat varies with climate, water-table position, and nutrient supply (Moore and Bellamy 1974).

Fig. 1: Picture of typical plant community of the Everglades http://www.classicrealism.com/landscape/html_1/Everglades%20Swamp.htm

2 Stephanie Möller, TU-Bergakademie Freiberg

Introduction The Everglades National Park is the largest remaining subtropical wilderness in the United States and ecologically linked with series of lakes, streams, swamps, and included freshwater and saltwater areas. The Everglades wetland environment extends southward from Lake Okeechobee to the Mangrove and Coastal Glades near Florida Bay and is located west of the Atlantic Coastal Ridge (Fig 2).

Fig. 2: Physiographic provinces of south Florida (Davis, 1943; Parker and others, 1955) http://sofia.usgs.gov/publications/circular/1134/


The Everglades are a result of marine and freshwater processes that have alternated with the rise and fall of sea level, which acted upon the Everglades basin defined by the eastern coastal ridge. With the recession of glaciers in North America at the end of the Pleistocene epoch, the rising sea level helped to retain water within the broad shallow Everglades limestone bedrock basin. This hydrology processes were favorable to the proliferation of the wetland environment and allowed thick accumulations of peat about 3-3.7m within the deeper parts of the basin (Stone and Gleason, 1983). The natural rhythms of the Everglades are supported by abundant precipitation and seasonal rainfall climate which were neccassary for the evolving of the wetland: Dry Season (approximately November-April), Transition Season (appr. May-July) and Wet Season (appr. August.October). Within the Everglades are eight habitats defined by climatic conditions: Marine/Estuarine, Coastal Prairie, Mangroves, Freshwater Slough, Cypress, Freshwater Marl Prairie, Hardwood Hammocks, Pineland (Fig. 3).

Fig. 3: Habitats of the Everglades defined by climatic conditions and watertabel position http://www.nps.gov/archive/ever/eco/habitats.htm The Everglades sediment record and radiocarbon dating of peats and some calcitic muds have revealed past vegetational stages and changes, including the development of tree islands (Stone and Gleason, 1983). Transgressive sequences of marine-brackish sediments overlying freshwater sediments indicates that the position of freshwater environments of about the same age related to the early Everglades period were more extensive to the south and southwest of the basin. Furthermore, the Everglades marsh also extended to the north into present Lake Okeechobee, which was remained on peat deposits underlying open water on the south end of the lake. Long-term hydrologic fluctuations and hydrologic conditions were suggested by the interbedding of peats and calcitic muds at various locations and depths within the Everglades. The importance of calcitic muds is the record of paleohydrologic facts because they indicates hydrologic conditions below the “wetness” threshold for formation and accumulation of peat. Environmental problems of the Everglades biosphere reservate (1976) and this world heritage site (1979) are indicated by water quality affected by suspended and dissolved organic and inorganc materials, a continuation in the rise of sea level that has occurred since the end of the last glacial maximum and human-caused overdrainage coupled with drought.


The Everglades Peatland Formation of the Everglades peatland began to form about 5500-5000 YBP (Fig. 4).Calcitic mud marshes deposited upon the Everglades basin with beginning of seasonal short-flooded areas (6500 YBP). Extensive areas of marsh peats indicates the widespread development of wetland environments including long hydroperiods supporting increase of peat and Freshwater wetland system of seasonal flooding (5000-4500 YBP).

Fig. 4: Soils of organic and recent limestone origin in south Florida (Fernald, 1981) http://sofia.usgs.gov/publications/circular/1134/


Geologic History of the Everglades Basin Marine and freshwater processes with the rise and fall of sea level have alternated the surficial geology of south Florida (Fig. 5). The Everglades has an almost imperceptible slope to the south. Deposition of limestone and creation of beaches and dunes occurred at high sea level. Creation of the riddled solution features characteristically of the region occured by drainage of acidic freshwater, that dissolved and eroded the limestone when sea level was low.

Fig. 5: Generalized surficial geology of south Florida (Puri and Vernon, 1964) http://sofia.usgs.gov/publications/circular/1134/


The rise in sea level slowed about 3,200 years ago, which was favored for the expansion of coastal and freshwater wetlands. Accumulation of thick layers of peat (up to 18 ft) within the northern parts of the Everglades basin due to retained freshwater in the basin by the Atlantic Coastal Ridge. The marine carbonate sediments in south Florida contain three major aquifer systems - the Floridan, the intermediate, and the surficial (Klein, 1972). Cretaceous and Tertiary carbonate rocks of Coastal Plain South Florida was isolated from the mainland. Limestone, dolomite and anhydrite were deposited in Cretaceous and Tertiary epoch as a carbonate platform. When the strait get filled, south Florida was connected to the mainland. The younger Tertiary deposit consisting of shallow marine sandy limestone, marls, and sands were formed of clastic sediments that are transported to the south. Marine sedimentary rocks, mainly carbonates, underlains the Everglades limestone bedrock. Miocene deposition of the Tamiami Formation Accumulation in Miocene epoch of a blanket of cream, white, and greenish-gray clayey marl, silt, sand and sandy marl (up to 100 feet thick) in area of south Florida. This Formation, consolidated and cemented into limestone, called Tamiami Formation makes up the bedrock surface of the northwestern area of the Everglades National Park. Pliocene emergence and slight erosion Only sandy and shally marls in the north area of the Okeechobee, which suggest that this area may have been at or above the sea level. Pleistocene deposition The Fort Thompson Formation is the unit of the lower pleistocene, very permeable with marine and freshwater marls, sandstones, and shelly limestones and the main water-bearing component of the Biscayne Aquifer. The Miami limestone, deposited during the last Pleistocene interglacial episode (preceding Wisconsinan glaciation), is a unit with two distinct facies: the oolitic facies Atlantic Coastal Ridge, the Everglades region, parts of the southern coast, Florida Bay, and the southern Florida Keys; the bryozoan facies southwestern and south central Florida.


Holocene mucks, soils, and sediments With recession of ice sheets of Wisconsinan glaciation, sea level rose fairly rapidly continuing into early Holocene epoch. Decrease of this rate in the past 4000-5000 years and sea level has risen more slowly. Accumulation of unconsolidated sediments followed upon the land surface of southern Florida. Weathered and eroded material of the Tamiami and Miami Limestones were spreaded by southward-flowing waters and occupied by the Everglades. Mixed with sediments are accumulated peat and muck soils. Formation of the Everglades Peatland The Calcitic Mud Calcitic mud is a freshwater, frequently shelly, nonstratified, low-magnesium calcitic silt (Gleason et al., 1974) and the oldest postglacial wetland sediment of the Everglades. It is found underlying wide areas of the peat deposit in the northern Everglades (Davis, 1946). The formation is suggested by precipitation of blue-green algae covered with calcium carbonate in submerged algal mats, called periphyton. Sparsely vegetated marshes with relatively shallow water for the photosynthesizing algae and considerable oxidation of organic material in the sediment are neccessary for the development of calcitic mud. The average floodwater depth for all present marl-producing / marl-floored areas in the Everglades vicinity is averaging 21.6 cm (Tropical Bioindustries, 1987). May-June through October-November includes the hydroperiod for those areas in Taylor Slough, located in the southern Everglades park and covered by calcareous periphyton and marl, depending on the beginning of summer rainfall (the Atlantic Hurricane Season, Transition and Wet Season). The environmental deposition occurs in areas with runoff high in calcium and bicarbonate concentration from nearby or distant limestone terrains and indicates an annual period of flooding at the time of deposition. Somewhat drier climatic periods were represented by calcitic mud horizons within Everglades peat profiles. Hydroperiod requirements for the deposition of calcitic mud are relatively short compared to those for marsh peat accumulation (P.A. Stone and P.J. Gleason, 1983). Gleason et al. (1974) indicate three reasons for the dominance of calcitic mud deposition rather than peats under short-hydroperiod marsh conditions.

- the less-wet conditions inhibit the luxuriant growth of plants that formed peat

- seasonal drying favors the precipitation of calcium carbonate as a result of concentrating calcium and carbonate ions by evaporation

- a long season of dryness promotes the oxidation and breakdown of organic material that would form peat.

The movement from peat to muck deposition suggests deeper water and probably longer stages of hydroperiods.


The oldest postglacial-age sediment of the Everglades (6470±120 YBP) were found below a muck-over-peat deposit on Kreamer Island in the south of Lake Okeechobee representing a former extension of the Everglades. Scholl et al. (1969) used radiocarbon dates to estimate the rate of calcitic mud deposition in present coastal areas and found evidence for a decrease with time. The rate averaged 2.8 cm/100 years from 5000 to 4000 years ago, 1.9 cm per 100 years from 4000 to 3000 years ago, 1.7 cm/100 years from 3000 to 2000 years ago, and 1.2 cm/100 years from 1000 years ago to present (P.A. Stone and P.J. Gleason, 1983). This decreasing rate of deposition is attributable to the decreasing rate of sea level rise, but this trend may instead reflect the decrease in subaerial exposures of limestone as the Everglades basin became filled with peat and the dissolving limestone in progressively higher areas was covered with peat and calcitic mud (Gleason et al., 1974). Peat deposition The deposition of peats is formed by the preservation of wetland plant communities with its roots, rhizomes, stems and leaves. The deposition of organic sediments and mucks originate from accumulation of fine peaty organic matter and fine sedimentary or detrital mineral material in a nearshore environment adjacent to or in Lake Okeechobee marshes. The adaption of plant communities and long-term changes in the development of the Everglades environment (hydroperiod, water flow, fire, floods, droughts, animal activity, formation of floating peat islands) provided the zonation of the peats (vertically and horizontally). The deposition of the peat formation began during the past 5000 YBP (5490 ± 90 YBP) dated by basal peat of the south end of Lake Okeechobee, which is the oldest freshwater peat yet dated from the Everglades. Process of deposition was nearly simultaneously from the south of Lake Okeechobee to the southeastern part of the Everglades (north of Waterconservation Area 2; W.A. are spatially and functionally central to water management and candidates for ecological revitalization, providing substantial downstream benefits to the Everglades, including Florida Bay). The long-term average rate of deposition was 8.4 cm per century increasing exponentially with time, determined by radiocarbon dating of peats (McDowell et al., 1969). The development of peat profiles was very slow in the beginning, but extended rapidly (7.3 cm per 100 years) from about 3500 to 1200 YBP. In the time after 1200 YBP the deposition was approximately 16 cm per 100 years in due to the slowing sea level rise. This increase suggests independent peatland processes and feedback mechanism. Various peat types and their association with particular plant community types were discussed by Davis (1946) and Jones et al. (1948), referred to soil series including several different sediment types and horizons in a profile, later associated more with characteristic sediment. Clayton et al. (1942) describe the Everglades peat depositions as follows:


brown to black in color, fibrous to granular, fairly low in mineral content (about 10% of the dry mass) and refers to sediments mainly formed from sawgrass. These peat types are the most abundant of the organic sediments, covered approximately 4420 km2 (1,091,000 acres) of the Everglades marsh. The black color of certain of these peats has been attributed to an abundance of charcoalized material (fusinite) from fires which swept through the Everglades throughout their history (Smith, 1968). Next one is the Loxahatchee peat which refers to peats derived from roots, rootlets, and rhizomes of the white water lily ( 2950 km²). Tree island peat, called Gandy peat, is a rooty and sometimes leafy peat formed by forest vegetation on Everglades tree islands (77 km²), which forms in the exposed oxidizing zone above surface water. Mainly distribution of marsh peat types, tree island or hammock peats are related to bedrock featured topography. The topographic expression of the bedrock surface with its four main features (one high and three low areas) appear to have had a profund effect on the type of vegetation and its prolonged development as revealed by peat type. The high area is overlain by Everglades peats and topped by sawgrass marshes. The low areas are depressions overlain by Loxahatchee peats, topped by water lily sloughs and mixed wet prairies interspersed with tree islands. In the northeastern, water lily-dominated parts of the Everglades there are two distinct types of tree islands that are abundant on the peat formation: red bay tree islands and dahoon holly tree islands. The predrainage flow through the Everglades controlled the shape of the Everglades tree islands and their associated peat depositions. Areal changes of the peatland or contracted marshes occurred with the transgressions of the respective shorelines, caused by the rise of sea and lake level, which is a natural consequence of hydrologic feedback. Surface water levels increase as the peat surface elevation increases – average water level rises with the peat surface (P.A. Stone and P.J. Gleason, 1983). Drainage systems and conversion to agriculture has now occupied much of the Everglades peat area. Peat production in Florida Florida ranks in the top five states of the United States in the production of horticultural peat. Furthermore peat is produced for agricultural and industrial purposes. In the ‘90s there were ten companies produce both reed-sedge and humus peat in seven counties (Fig.7). Moisture content of peat deposits may affect the properties and uses. Peat deposits can be naturally dry, or may have been drained (Fig.6). Dewatering by trenching makes it possible that peat support the shovels, draglines, and earthmoving equipment used in the mining operations. Further processes of mining are excavation, transferred to storage for drying, followed by shredding. During the 1970’s the potential uses of peat as fuel were evaluated and a Department of Energy study published in 1980 covered the potential for producing liquid fuels from peat. Since 1980 the interest in developing using peat for energy


purposes has diminished. In 1990, in Maine a small power plant (23 MW) was constructed to be fuelled by local peat. Association of initial problems with the use of inappropriate harvesting equipment were overcome. But it was then difficult to obtain further permits to exploit the larger bog area that was required. Now, the boilers are mainly fuelled by wood chips. At present, there were proposals for three or four small peat-burning power stations (aggregate capacity 360 MW) to be built in Florida for using peat in electric-power production, but it is primarily conducted on private lands. Problems of peat mining occures with drainage and oxidation of peaty soils, contaminating wetlands with nitrates. The commodity of economic and industrial minerals of Florida are petroleum and natural gas, phosphate rocks, crushed stone, cement, limestone, sand and gravel, clays, heavy minerals and peat (Fig.7). Conclusion

The Everglades peatland was formed during the last 5000 years at the end of the Pleistocene age, after the world-wide climatic changes and sea-level rise and is supported by a freshwater wetland system of seasonal flooding and dominated by marshes with scattered tree islands. The south Florida ecosystem consists primarily of wetlands and shallow water habitats set in a subtropical environment. Water drained slowly to the south through what was referred to as the "River of Grass" by Florida author and conservationist Marjory Stoneman Douglas. The oldest postglacial wetland sediment dated from the Everglades is calcitic mud. Organic sediments, peats, and mucks originate from the preservation of wetland plant communities in the case of the peats or formed in a nearshore environment adjacent to or in Lake Okeechobee in the case of muck deposits. The Everglades National Park today serves as both an example and a warning. No other subtropical or tropical wetland enjoys such overt recognition of biological importance like the Everglades, recognized on three international lists – International Biosphere Reserve, World Heritage, and Ramsar Convention. The importance of this ecosystem is the unique of the complexity of the hydrological and biological system. Today 50% of South Florida’s original wetland areas no longer exist. The degradation of the natural system is affected by human-caused overdrainage coupled with drought and conversion to agriculture.


Fig. 6: Dewatering of Hurley Peat Mine, Lake County, Florida http://www.sjrwmd.com/govboard/pdfs/2006/rg0604/rg0604_006.pdf


Fig. 7 : Mine locations in Florida http://www.dep.state.fl.us/geology/geologictopics/minerals.htm


References Randazzo, Jones (1997) The Geology of Florida, University Press of Florida Davis, Ogden (1997) Everglades – The Ecosystem and Its Restoration, St. Lucie Press Harris, Tuttle, Tuttle (1997) Geology of National Parks, Kendall / Hunt Puplishing Company http://sofia.usgs.gov/publications/circular/1134/index.html http://www.schulz-naturphoto.de/galerie-everglades-1.htm http://www.nps.gov/ever/ http://minerals.usgs.gov/minerals/pubs/commodity/peat/510499.pdf http://fulltext10.fcla.edu/cgi/t/text/text-idx?c=feol&idno=UF00000469&format=pdf http://www.dep.state.fl.us/geology/geologictopics/minerals.htm http://www.sjrwmd.com/govboard/pdfs/2006/rg0604/rg0604_006.pdf

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The Everglades National Park – Evolution of the Everglades ... · The Everglades National Park – Evolution of the Everglades Peatland Stephanie Möller TU-Bergakademie Freiberg